1. length l: main unit: meter; ? Measuring tools: scale estimation The next smallest unit of measurement in reading is the length unit.
Time t: unit: second; Measuring tools: laboratory watches and stopwatches. 1:00 = 3600 seconds, 1 second = 1000 milliseconds.
3. mass m: the quantity of purpose contained in this substance is called mass. Unit: kg; Measuring tool: scale; Balance of laboratory trays.
Second, mechanical movement.
Moving machine: the movement of changing position of an object.
Reference: To determine the motion of one object, another object must be selected as the standard. This is the selection criterion called reference object.
3. Uniform linear motion:
(1) Comparison of two methods of moving speed: one died at the same time. B compare the time required to get away from the equation.
② formula:1m/s = 3.6km/h.
Third, force.
1. Force f: the object of the force object. The intermolecular interaction of body force is always mutual.
Unit of force: Newton (n). Instrumental force measurement: force; Spring scale for laboratory use.
Effect: the stress state of object deformation changes, and the object moves or produces.
The changing state of a moving object means that the speed or moving direction of the object changes.
3. The three elements of force: force? The magnitude, direction and action point of force are called the three elements of force. (on the same object)
The power of icon makes it have scale and direction; Schematic diagram of force, scale-free.
3. Gravity G: the attraction of celestial bodies. Direction: straight down.
The relationship between gravity and mass: G = M = G/G mg
G = 9.8 N/kg. Reading method: 9.8 newtons per kilogram, and the gravity of a kilogram of objects is 9.8 newtons. (g) There is no special explanation for junior high schools that are different from the latitude and longitude of the earth. Generally, it needs 9.8, and high school generally needs 65,438+00, except for countless Shanghai deaths in 2007. To this end, the main check is to keep two decimal places. )
Center of gravity: The function of the center of gravity is called the center of gravity. The center of gravity of an object is in the geometric center law of an object. (There are two ways to hang the center of gravity of irregular objects)
2. Two-force equilibrium conditions: the action of the same object; Two equal and opposite forces act on a straight line.
The balance of two forces borne by an object can be static, but it can also be used for uniform linear motion. (i.e. equilibrium state)
The goal of balance is that the object is stationary or moving at a uniform speed. The external force of a balanced object is zero.
Two resultant forces: ⒌ the resultant force of the same line in the same direction F = F 1+F2, the direction of the resultant force F 1, the direction of F2;
The force in the opposite direction is F = F 1-F2, and the direction of this force is the same as that of the large force.
Under the same conditions, rolling friction is much smaller than sliding friction. (Maximum static friction is greater than sliding friction)
The positive pressure, contact surface and roughness of sliding friction are related to the material characteristics. Sliding friction, rolling friction, static friction]
7。 Newton's first law, also known as the law of inertia: all objects come from external forces and always remain stationary or move in a straight line at a constant speed. Inertia: The property that an object maintains its original static or uniform linear motion is called inertia. (Inertia is the property of gravity, and the density ratio of heat is the property of objects. )
Fourth, density.
1. Density ρ: the mass per unit volume of a substance, and density is a characteristic of the substance. The density of some common densities of water is 1. If you are interested in different temperature conditions, you can learn and only remember the test line.
Formula: m =ρV International unit: kg/m3, common unit: g/cm3,
Relationship:1g/cm3 =1x103kg/m3, ρ water =1x103kg/m3;
Reading: 103kg/m3 The mass of water is 103kg.
1. Density measurement: the tray balance measures the mass, and the measuring cylinder measures the volume of solid or liquid.
Area unit conversion:
1 cm2 = 1× 10-4 m2
1mm = 1× 10-6m。
Fifth, stress.
1. pressure p: the pressure exerted by an object per unit area is called pressure.
Pressure f: an object with a force perpendicular to the surface, in N. ..
Force, pressure, pressure, pressure effect.
Pressure: n/m2; Special name: Pascal (Pa)
Formula: F = PS [S: stress area, in the common part where two objects contact; Unit: square meters.
Methods of pressure change: (1) Reducing the pressure or increasing the stress area can reduce the pressure; (2) Increasing the pressure or reducing the stress area can increase the pressure.
1. Liquid internal pressure: measuring liquid: liquid internal pressure measuring tube (U-shaped tube for pressure measurement).
Reason: The pressure generated by gravity at the bottom of the liquid container is due to the pressure of the liquid flowing wall.
Methods: ① The pressure in each direction is equal to the pressure in the same depth. (2) the greater the depth, the greater the pressure, the same depth. (3) Different liquids have higher liquid density and pressure. Depth h is the vertical height from a point to the liquid level. ]
Formula: P =ρghH: unit: meter; ? ρ: kg/m3，G = 9.8 N/kg。
13. Atmospheric pressure: the pressure generated by gravity in the atmosphere, the existence of atmospheric pressure and the measurement of atmospheric pressure. Has the experiment in the hemisphere of Fort Madre proved it? Torricelli (Italian scientist). When the Torricelli tube is tilted, the height of the mercury column remains unchanged and the length becomes longer. (This experiment uses the reason that the water column of Mercury 10 meter high. )
A standard atmospheric pressure = 76 cm Hg height = 1.0 1× 105 Pa = 10.336 m H2O.
Means of measuring the atmosphere: barometer (mercury barometer, box barometer).
Atmospheric pressure varying with height: the higher the height, the smaller the atmospheric pressure, and the lower the boiling point with the increase of height.
VI buoyancy
1。 Buoyancy and reason: An object immersed in liquid (or gas) is called buoyancy. It is made of liquid (or gas). Direction: vertically upward; Cause: the pressure difference between the upper and lower parts of liquid objects.
2。 Archimedes principle: When an object is immersed in a liquid, the buoyancy of upward buoyancy is equal to the gravity of the object displacing the liquid.
F float = G line = ρ liquid GV line. (Line V represents the displacement liquid volume of the object)
3。 Buoyancy formula: f float = GT =ρ line GV of ρ fluid = f, pressure difference.
4。 When the object floats: f float = G and ρ
When the object floats: f floats >; G and ρ content
Seven, simple machinery
1. Lever balance condition: F 1L 1 = F2L2. Force arm: the vertical distance from the fulcrum to the line of force action.
The purpose of adjusting the nuts at both ends of the lever to make the position of the lever in the water is to facilitate the direct measurement of the length of the power arm and the resistance arm.
Crown block: Equivalent to, can't sum energy, but can change the direction of force.
Moving pulley: the power arm is twice as large as the resistance arm, which can save half of the power, but you can't change the direction of the power.
2. Force: two necessary factors: ① the force acting on the object; ② The force of an object in the direction of distance. W = unit of fs activity: joule.
3。 Power: the object of work done per unit time. The physical quantity of the object, that is, the object of the power supply, acts quickly.
W = PT P:W； W unit: joule unit is t: s.
Baguang
Light travels in a straight line, and light travels in a uniform medium. Phenomenon pinhole imaging, shadow and projection light travel in a straight line.
The light speed under the maximum vacuum is 3×108m/s = 3×105km/s.
The law of light reflection: two sides. 【 Angle between incident light and normal incident angle. The angle between reflected light and normal reflection angle.
Imaging characteristics of plane mirror: virtual image, large and equidistant from others, symmetrical with mirror surface. The object in the reflection in water is the reflection of virtual image light.
3. Refraction phenomenon and the law of light: when you see chopsticks in water, the refraction phenomenon of virtual image light of fish. In fact, if you draw a refraction prism of light, it is no problem to find out this kind of light. )
A convex lens focuses light, while a concave lens diverges light. The law of refraction of light: three aspects shared by both sides.
3. The law of convex lens imaging: U = F imaging ≤ = 2fv = 2f into an inverted real image]
Application of natural light path diagram Object distance diagram
The F<V & lt2F on the second floor of U> reduced the real-time image camera.
F<U & lt2F V & enlargement of GT2F inverted real-image slide projector
ü& lt； F vertical virtual image is a magnifying glass, zoom in.
U = F is neither a real image nor a virtual image.
U = 2F Invert the real image (vertically invert the real image, virtual image, understand this line. )
Convex lens imaging experiment ⒌: Put it on the optical seat of candle, convex lens and light screen in turn, so that the center of Zhu Yan of biconvex lens is at the same height as the center of central light screen.
Nine, thermal energy:
1. temperature t: indicates the degree of heat and cold of the object. [Status amount.
The principle of ordinary thermometer: according to the characteristics of liquid thermal expansion and cold contraction.
Thermometers at different points and the minimum calibration of thermometers: ① range, ②, ③ glass bulb, curved tubule.
The heat transfer condition is: temperature difference. Heat: the heat absorbed or released by an object during heat transfer. [throughput]
Heat transfer modes: conduction (heat transfer along objects), convection (heat transfer through the flow of liquid or gas) and radiation (heat directly released by high-temperature objects).
3. Vaporization: The removal of a substance from a gas in a liquid. Mode: evaporation and boiling endothermic vaporization.
The factors that affect the evaporation rate are (1) liquid temperature, (2) liquid surface area and (3) liquid surface air velocity. Evaporative refrigeration.
2. Specific heat capacity C: The specific heat capacity of a substance per unit mass when the temperature rises by 65438 0℃ is called the absorbed heat.
The specific heat capacity of a substance is 1, and the unit is kilojoule/(kg℃) of the specific heat capacity of water of an ordinary substance.
C water = 4.2× 103 J/(kg C) reading: 4.2× 103 joules per kilogram of celsius.
Physical meaning: The temperature of water with the mass of 1 kg rises 1℃, and the heat absorbed is 4.2× 103 Joule.
⒌ heat: Q = cm ⊿TL discharge = cm ⊿T drop Q suction.
Q is inversely proportional to c, m, ⊿T is directly proportional to c, m, 1⊿T.⊿T = Q/cm.
6。 Internal energy: the sum of kinetic energy and molecular potential energy of all molecules of an object. All the energy in the body. Internal energy unit: Joule
The internal energy of an object and its temperature. When the temperature of an object increases, the internal energy increases; The temperature in the room can be reduced.
Changing an object: energy and heat transfer in action (equivalent to changing an object)
7。 Conversion of conservation energy: energy is not a vacuum, it will not suddenly disappear, it will only change from one form to another, or from one object to another, and the total energy will remain unchanged.
10, circuit
The circuit consists of power supply, electric key, waste electrical appliances, wires and other components. In order to make the circuit continuous, the circuit must have a power supply circuit, which should be closed. Circuit access, open circuit (open circuit), power supply and electrical short circuit.
2. A substance that conducts electricity easily is called a conductor. Like metals, acids? Alkali is an aqueous solution of salt. Substances that do not conduct electricity easily are called insulators. Such as wood, glass, etc.
Under certain conditions, an insulator can be transformed into a conductor.
3. Identify series and parallel circuits: parallel series: current divergence: current divergence.
The method of converting standard circuit diagram into standard circuit diagram: the path through which current flows.
XI current law
1. Electricity Q: How much charge is called unit of power Coulomb.
I: 1 sec power passing through the conductor section is called current intensity. Q =
Unit of current: ampere (A) 1 A = 1000 mA The direction of positively charged directional motion current is defined as.
The measuring current is connected in series with the ammeter in the circuit, and the range to be considered is appropriate. An ammeter that allows direct connection to a power supply.
2. Voltage U: The reason why the directional movement of free charge forms a current loop. Voltage: voltage (v).
Use a voltmeter (voltmeter) to measure the voltage across the circuit (electrical appliances, power supply) within the parallel range, and consider it appropriate.
3. Resistance R: current barrier of conductive objects. Symbol: r: ohm, kiloohm, megaohm.
The size of the resistance is directly proportional to the length of the wire, and the cross-sectional area (thickness) is inversely proportional to the material.
Different conductor resistances are connected in series in the circuit with the same current (1: 1). Conductor resistances are connected in parallel in the circuit with the same voltage (1: 1).
3. ohm's law: formula: I = u/ru = IR r = u/i.
Conductivity with conductor? The intensity of current in the body is directly proportional to the voltage at both ends and inversely proportional to the conductor resistance.
Conductor resistance R = U/IA The conductor determines whether the voltage changes and the current changes, but the resistance value remains the same.
5. Series circuit characteristics:
①I = I 1 = I2②U = U 1+U2③R = R 1+R2④U 1/R 1 = U2/R2
With different series resistors, the voltage across the resistors decreases with the size of the conductor resistances of the two conductors.
6. The characteristics of parallel circuit:
① u = u1= u22i = I1+I 231/r =1+1R2 or 4i1r/kloc.
Two wires with different resistance values are connected in parallel, and the conductor with large current passes through the resistor with smaller resistance.
For example, the ammeter with R2 =6 shows a K-drop of 0.4 K. 1.2 A ... Find: ① the power supply voltage of r1resistor ② the total resistance (3).
Twelfth electric power
1. power w: it works by the so-called electric current. The process of current supply is to convert electric energy into other forms of energy.
Formula: W = UQ W = UIT = U2T/R = I2Rt W = PT Unit: W Joule ≤ Volt, I Ampere, T Seconds, Q Library, P Watt.
2. Electric power P: It consists of current and electric power per unit time, indicating the speed at which current is used for power supply. Large current is faster to supply power.
Formula: P = W/TP = UI(P = U2/RP = I2R) Unit: W Joule ≤ Volt, I Ampere, T Seconds, Q Library, P Watt.
3. Watt-hour meter: Measure the power consumption of instruments. 1kwh =1kwh =1000 watt (rated voltage and actual voltage, rated short-circuit current, common problems of voltmeter and ammeter in the exam.
13, magnetic
1。 Magnets, like poles repel, like poles attract]
The property that an object can attract iron, cobalt, nickel and other substances is called magnetism. Magnetic materials are called magnets. Magnetic poles always appear in pairs.
2。 Magnetic field: it exists in the space around the magnet, and other magnets play a role.
The basic properties of magnetic field produced by magnets.
The direction shown is the direction of N-pole magnetic field: small needle fixing point. The magnetic lines of the magnetic field around the magnet.
Geomagnetic north pole is close to geographical south pole, and geographical north pole is close to geomagnetic south pole.
3。 Current magnetic field: Oster's experiments show that current exists around the magnetic field.
The coil is equivalent to a bar magnet.
The relationship between the current direction in the stressed solenoid and the polarity at both ends of the solenoid can be determined by the right-hand spiral law.
(Remember, the right hand blackens the N pole. )
formula
Part of the Force. ]
1, speed: = S/T
2. Gravity: G = mg
3. Density: ρ = m/v.
4. Pressure: P = F/S mode
5. Liquid pressure: P value = rhogh
6. Buoyancy:
(1), f float = F'-F (pressure difference)
(2), f float = G-F (depending on gravity)
(3), F floating = G (floating suspension)
(4) Archimedes principle: F = G row = ρ liquid GV row floats.
7. Lever balance condition: F 1 L 1 = F2 L2.
8. Ideal slope: F/G = H/L
Ideal pulley of 9: F = G/N
As shown in figure 10, the actual pulley: F =(G+G activity)/positive (vertical direction).
1 1, function: W = FS = GH (lifting the height of the object)
12, power: P = W/T = FV.
13, working principle: w hand = W machine.
As shown in figure 14, actual machinery: W = W+W extra.
15, mechanical efficiency: η = the sum of w/w.
16, pulley block efficiency:
(1), [η] = G/nF (vertical direction)
(2), η= G /(G+ G activity) (without considering the friction in the vertical direction)
(3), [η] = f/nF (horizontal direction)
[Hot parts]
As shown in figure 1, heat absorption: absorption rate q (ton-t0) = cm = cm δ t.
As shown in figure 2, exothermic: Q? Put = Cm (t0 to ton) = cm δ t
3. calorific value: Q = Q/M
4. Efficiency of furnace and heat engine: η= qeeffective/q fuel.
5. thermal balance equation: q-discharge = Q-suction.
6. Thermodynamic temperature: T = T +273 K table.
[electricity, part]
1, current intensity: I = Q power supply/ton
2. Resistance: R =ρL/ S
Ohm's law: I = U/R
Joule's law:
(1), Q = I2Rt general formula)
(2), Q = UIT = PT = UQ electricity = U2T/R (pure resistance formula)
5 series circuits:
( 1)，I = I 1 = I2
(2)，U = U 1 + U2
(3)，R = R 1+R2。
(4), U 1/U2 = R 1/R2 (partial pressure type)
(5)，P 1/P2 = R 1/R2
6 parallel circuit:
( 1)，I = I 1 + I2
(2)，U = U 1 = U2
(3)， 1/R = 1/R 1+ 1/R2[R = R 1 R2/(R 1+R2)]
(4)I 1/I2 = R2/r 1 (shunt type)
(5)，P 1/P2 = R2/R 1
Seven fixed-value resistors:
( 1)，I 1/I2 = U 1/U2
(2)，P 1/P2 = I 12/I22
(3)，P 1/P2 = U 12/U22
8 motor power:
(1), W = UIT = PT = UQ (general formula)
(2), W = I2Rt = U2T/R (pure resistance formula)
9 motor power:
(1), P = W/T = UI (general formula)
(2), P = I2R = U2/R (pure resistance formula)
【 Law of Exercise 】
In figure 1, the speed of light is C = 3× 108/s (vacuum).
2. The sound speed is V =340/s (15℃).
3. Echo resolved by human ear: ≥0. 1 sec.
4. Gravity acceleration: G = 9.8N/kg≈ 10N/kg.
5, the value of the standard atmospheric pressure:
760mmhg =1.01×105pa height.
As shown in Figure 6, the density of water is ρ= 1.0× 103kg/m3.
As shown in Figure 7, the freezing point of water: 0℃
As shown in Figure 8, the boiling point of water is 100℃.
9. Specific heat capacity of water:
C = 4.2× 103J/(kg？ ℃)
10, elementary charge: e =1.6×10-19c.
1 1, dry cell voltage:1.5v.
As shown in figure 12, the voltage of lead-acid battery is 2V.
13, for human safe voltage: ≤36V (not higher than 36V).
14, power supply circuit voltage: 380V V v.
15, household circuit voltage: 220V.
16, unit conversion:
(1), 1 m/s =3.6 km/h.
(2), namely 1g/cm3 = 103K.
One more question.
Fill in the blanks: (25 points)
A pulling force F with a weight of 100 N acts on an object to move horizontally in a straight line at a uniform speed, and the friction force generated by strenuous work is _ _ _ _ _ _ _ _ _ _ _ _ _. Work done by gravity on _ _ _ _ _ _.
As shown in the figure, the lightweight rod OB is still in the horizontal position, with BO = 2OA. If gravity acts on the object C to the power of100th Newton, the force F _ _ _ _ _ _ _ Newton.
Here is a labor-saving lever: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. Scale, fishing rod, barber scissors, iron scissors, crown block, moving pulley.
As shown in fig. 4, objects A and B are subjected to the gravity of 1000 Newton, excluding the pulley gravity. When the force is uniform, the elevator objects are A and B, the force FA _ _ _ _ _ _ _, and the force FB _ _ _ _ _ _.
5 Power: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Power: _
The reason of pulley block is to introduce extra work, because two factors are considered: _ _ _ _ _ _ _ and _ _ _ _ _.
7 The crane speed is 0.2m/s, and the cargo weight increases 10m. The crane works in ________ W, totaling in _ _ _ _ _ _ _. Put it on and rotate it horizontally for 20 meters. The crane completes this process as follows: _ _ _ _ _ _ _.
Someone uses a pulley to lift a 400-Newton object evenly, and the moving distance of the free end of the rope is 10 second. The action of tension and tension is _ _ _ _ _ _ _ _ _ _ _ The power is 250 N, and the useful work is _ _ _ _ _ _.
9。 Satellite transfer from apogee and perigee, gravitational potential energy _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
10 indicates what the following objects may be:
(1) cars running on the road (2) the sky of the plane;
(3) apple trees; (4) Tension spring
2。 Multiple choice questions: (18 points)
1, as shown in the figure, the rod can be hung on the weight of the lever around the O point. In order to improve the weight, the force f perpendicular to the straight bar and the vertical position of the opposite sex slowly rotate to the horizontal position. In this process, the straight rod ().
(a) It has always been a labor-saving lever; (b) It is always used effortlessly.
(c) First, it saves labor. (d) After the first attempt, it is effortless.
2, the most labor-saving power is
(A)F 1(B)F2(C)F3(D)F4
Using simple machinery, the following statement is correct:
(a) You can save electricity (b) instead of saving electricity.
(c) It can save labor, but it is also above the provincial level. (d) There are many mistakes.
4. Movable pulley used ()
(a) The effort to exert force in the direction (b) can be changed without effort, and the deviation from the direction cannot be changed.
(c) With hard work, they can change the deviation in direction (d), but not in direction (d).
5, the following statement is correct ()
The faster the mechanical work, the higher the mechanical efficiency (a) and (b), and the more machines, the higher the mechanical efficiency.
(c) The greater the mechanical power, the more powerful the mechanical work. (d) The speed of taking action.
As shown in fig. 6, a car with a weight of 600 N on the horizontal plane moves forward at a uniform speed when the pulling force is 60 n 6 m. In the process ().
(a) The resistance value of automobile resistor is 600N(B) The resistance value of automobile resistor is 100 N.
(c) Working Coke 360(D) The car-drawn cart is together with 3600 Coke under the action of gravity.
7. Even rainfall: ()
The reduction of kinetic energy can reduce the machine (b) potential energy decreases and kinetic energy increases;
(c) the rate constant that may be reduced (d) may reduce the constant mechanical energy;
8. In the following actions, part of kinetic energy is converted into potential energy:
(1) It is the pendulum of the pendulum. (b) The high jumper's landing point on the horizontal bar is from the bottom.
(c) Accelerate the car to run in a straight line on the road (d) Tighten the watch spring to drive the pointer to move.
9, one of the following circumstances, the role of force on the object is: ()
(B)(A) Being forced to play football while holding a heavy object still.
(D)(C) Maintain the constant weight of the crane on the horizontal ground to lift the weight into the air and move horizontally.
3。 Plot title (24 points);
1。
2,
. Inference title:
Why is the mechanical efficiency of pulley block less than 1? (4 points)
The energy conversion process of bicycle downhill is analyzed. (4 points)
5。 Question:
1, the picture shows a problem solved. The mechanical efficiency of 8000-Newton pulley block is 80%. It is required to lift the heavy objects by two meters in six seconds. It is required to lift the heavy equipment: (10 minute)
(1) How much tension is needed? (2) nervous?
2. The horizontal road weighs 5000, and the force of 100 Newton is even. Pushing 20 meters forward in 5 seconds is intense work? What's the motive? How much work has gravity done? (6 points)
3. As shown in the figure, within 1 minute, the weight of a 480-N object and the uniform pulley block is increased by 3 meters. If the mechanical efficiency of the pulley is 80%, it is found that: (1)-(2) total power) F(3) tension. (9)
Try to do this, and no one answers! Sorry, I can't find it.